The present invention relates to a transfer method and device and a driving system therefor for transfer presses.
Prior to the detailed description of the present invention, a conventional transfer device will be described with reference to FIGS. 1 and 2 so as to point out the technical problems thereof which the present invention contemplates to solve. A pair of vertically movable frames 1 and 2 (to be referred to as "lift frames" hereinafter in this specification for brevity) are disposed on both sides of an die array comprising a plurality of dies and extend in the direction of the processing line in parallel with each other. A plurality of movable stands 3 and 4 which can move in the direction of the processing line are mounted on the lift frames 1 and 2 and interconnected such that the distance between the adjacent pairs of movable stands 3 and 4 is maintained substantially equal to the distance between the adjacent die or processing stations and the movable stands 3 and 4 are drivingly coupled to a driving system (not shown) such that they are reciprocable in the direction of the processing line. A pair of supporting stands 5 and 6 which are reciprocably movable toward or away from each other in the direction of the processing line are mounted on the pair of movable stands 3 and 4 and cross bars 7 and 8 are mounted on the opposing supporting stands 5 and 6, respectively. A plurality vacuum cups 9 which can releasably suck a blank sheet are mounted on the cross bars 7 and 8. Reference numeral 10 represents pressed works.
With the transfer device with the above-described construction, after the works 10 have been pressed at the upstream die station A, the lift frames 1 and 2 are upwardly moved; while the cross bars 7 and 8 which were maintained at the retracted positions adjacent to the intermediate position C are moved away from each other, the movable stands 3 and 4 are moved to the station A. Thereafter the lift frames 1 and 2 are downwardly moved to lower the cross bars 7 and 8 toward the works 10 at the station A and then the vacuum cups 9 are activated to make the works 10 abut on the cross bars 7 and 8. Next the lift frames 1 and 2 are upwardly moved and the movable stands 3 and 4 are moved in the downstream direction to transfer the works 10 to the downstream die station B. Then the lift frames 1 and 2 are lowered and the vacuum cups 9 are released so that the works 10 are lowered and placed at the downstream station B. Thereafter the lift frames 1 and 2 are again upwardly moved; while the cross bars 7 and 8 are caused to move toward each other, the movable stands 3 and 4 are moved back to the intermediate position C. Then the lift frames 1 and 2 are lowered while the cross bars 7 and 8 are retracted, the works 10 being further pressed at the downstream die position B.
As described above, in response to the periodic actions of the lift frames 1 and 2, the movable stands 3 and 4 and the supporting stands 5 and 6, the cross bars 7 and 8 are caused to move vertically, transfer the works 10 and move toward or away from each other so that all the works 10 are sequentially transferred in the downstream direction and automatically pressed at a plurality of die or processing stations.
The transfer device with the above-described construction includes, as best shown in FIG. 3, a first driving device for vertically moving the lift frames 1 and 2, a second driving device for reciprocating the movable stands 3 and 4 in the direction of the process line and a third driving device for reciprocating the supporting stands 5 and 6 in synchronism with the movement of the movable stands 3 and 4 and causing them to move toward or away from each other on the movable stands 3 and 4. Thus, a driving system for driving the transfer device comprises the first, second and third driving devices. More specifically, the first driving device for vertically moving the lift frames 1 and 2 comprises a horizontal rack 11 which is drivingly coupled to a power source (not shown) for its horizontal movement, a pinion 12 in mesh with the horizontal rack 11 and a vertical rack 13 in mesh with the pinion 12 with the upper end thereof being securely joined to the lift frame 1 or 2, whereby the lift frames 1 and 2 are vertically movable through the pinion 12 and the vertical rack 13 by the horizontal movement of the rack 11.
The second driving device for driving the movable stands 3 and 4 comprises a carriage 15 which is located at one end of the lift frames 1 and 2, connected to the movable stands 3 and 4 through a connecting rod 14 and is reciprocable in the direction of the processing line and a feed lever 20 whose upper portion is vertically slidable in a vertical groove 16 formed in the carriage 15, and which is pivoted about a pivot pin 17 and carries a cam follower 18 at its lower end in contact with a feed cam 19 so that when the feed cam 19 is driven, the feed lever 20 is caused to pivot about the pivot pin 17 with its upper portion being slided along the groove 16. The swinging movement of the feed lever 20 is translated into the movement of the carriage 15 in the direction of the processing line, whereby the movable stands 3 and 4 can be driven.
The third driving device for causing the supporting stands 5 and 6 on the movable stands 3 and 4 to be movable in the direction of the processing line, thereby causing the cross bars 7 and 8 to move toward or away from each other, comprises a cam plate 27 attached securely to the lift frames 1 and 2 and having closed-loop-like cam surface means consisting of a downwardly directed cam surface 21, a reversal cam surface 22, an upwardly inclined cam surface 23, an upwardly directed cam surface 24, an upwardly inclined cam surface 25 and a second reversal cam surface 26; an inverted-T-shaped lever 33 which is pivoted at a midpoint between its lower ends to the carriage 15 with a pivot pin 28, has at its one lower end a cam follower 29 in rolling contact with the above-described closed-loop-like cam surface means (21-26) and a bias cylinder 30 at the other lower end for pressing the cam follower 29 against the cam surfaces 21-26 and is connected to a pushing-pulling rod 32 whose one end is slidable in an arcuate groove 31 formed through the upper end portion as will be described in more detail hereinafter, and said push-pull rods 32 which extend through the movable stands 3 and 4 such that they are reciprocable in the direction of the process line, thereby imparting the driving force to the supporting stand 5 and to the supporting stand 6 through a rack 34, a pinion 35 and a horizontal rack 36, whereby the swinging movement in the direction of the processing line of the lever 33 in unison with the carriage 15 is translated into the movement of the push-pull rods 32 in the direction of the processing line, thereby causing the supporting stands 5 and 6 on the movable stands 3 and 4 movable in the direction of the processing line to move toward or away from each other so that the cross bars 7 and 8 are also forced to move toward or away from each other.
A cylinder 37 changes the displacement of the push-pull rod 32 when the pivotal point of the push-pull rod 32 with respect to the lever 33 is changed to swing the lever 33.
The above-described transfer method and device and a driving system therefor for transfer presses have various technical problems. Firstly, great driving force is required for vertically moving the lift frames 1 and 2 which are long in length and heavy in weight. Furthermore, it is impossible to increase the speed of the processing line for improvement of the productivity since such speed increase would cause vibrations or oscillations of the lift frames 1 and 2 which are long in length and very heavy in weight when the works 10 are being transferred, resulting in dropping of the works 10 from the vacuum cups 9. Moreover, stroke of the cross bars 7 and 8 cannot be increased by the cam plate 27 because of the complicated construction of the cam plate 27 for causing the bars 7 and 8 to move toward or away from each other.
In view of the above, a primary object of the present invention is to make the lift component parts of a transfer device compact in size and light in weight, thereby decreasing the driving force, preventing vibrations or oscillations and making a transfer driving system simple in construction.